JPS6124905A - Controller for starting of boiler - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a boiler startup control device for controlling the startup of a boiler system.

[Background of the invention]

To start the boiler, after completion of startup preparations, the fuel system is operated, the burner is ignited, and the pressure and temperature of the boiler begins to rise. In this case, it is necessary to perform appropriate start-up control so that various parts of the boiler device do not overheat or excessive thermal stress is generated in thick-walled parts. Hereinafter, conventional activation means will be explained with reference to the drawings.

FIG. 17 is a system diagram of a conventional boiler startup control device.

In the figure, 1 is a water wall constituting the boiler furnace wall, 2 is a burner, and 6 is a boiler water supply pump that supplies water to the water wall 1.

Reference numeral 4 denotes a steam/water separator, which separates a steam/water mixture produced by heating the feed water on the water wall 3 into steam and moisture. 5 is a superheater that superheats the steam from the steam-water separator 4; 6 is an energy saver that preheats the water supplied from the water supply pump 6; and 7 is a turbine connected to the generator. Reference numeral 8 denotes a turbine control valve that is interposed between the superheater 5 and the turbine 7 and controls the amount of steam flowing from the superheater 5 to the turbine 7. 6o9 is a superheater that releases the steam from the steam separator 4 to a condenser or the like. It is a bypass valve. When a large amount of low-temperature steam flows into the superheater 5 during startup and prevents the temperature from rising at the outlet of the superheater 5, the superheater bypass valve 9 releases such low-temperature steam and shuts down the superheater 5. It has the function of reducing the passing steam cap and increasing the steam temperature at the outlet of the superheater 5. Reference numeral 10 denotes a turbine bypass valve for releasing the generated steam from the outlet of the superheater 5 to a condenser or the like. This turbine bypass valve 10 has a function of letting the generated steam escape when the temperature and pressure of the generated steam have not been increased to a level that allows ventilation to the turbine 7. When the steam flow rate is small, it becomes difficult to control the steam pressure based on the amount of fuel input, so it also has the function of contributing to steam pressure control by releasing the generated steam in this region.

11 is a steam pressure detector that detects the pressure of steam supplied from the superheater 5 to the turbine 7; 12 is a steam pressure setting device that sets the target pressure of the steam, that is, the target steam pressure;
13 is a subtracter which calculates the difference between the value set in the steam pressure setting device 12 and the value detected by the steam pressure detector 11. 14 and 15 are proportional integrators that proportionally integrate the pressure deviation signal calculated and output by the subtracter 13. 16 is a function generator which inputs the value detected by the steam pressure detector 11 and outputs a predetermined value corresponding to this value. The output signal from the function generator 16 becomes an opening command signal that commands the opening of the turbine bypass valve 10 to make the steam pressure appropriate. 17 is a function generator which inputs the value detected by the steam pressure detector 11 and outputs a value corresponding to this value. The output signal from the function generator 17 becomes an opening degree command signal that commands the opening degree of the superheater bypass valve 9 in order to make the steam pressure appropriate.

18 is a signal switch equipped with terminals 18α, 18b and a switching piece 18c, the terminal 18α is connected to the ratio flJ integrator 14, the terminal 18b is connected to the function generator 16, and the switching piece 18c is connected to the turbine bypass valve 10, respectively. has been done. 19
is a high signal selector which compares the output signal of the proportional integrator 15 and the output signal of the function generator 17 and outputs the larger signal to the superheater bypass valve 9. 20 is a fuel flow control valve that controls the fuel supply to the burner "2," and 21 is a fuel flow control valve that controls the opening degree of the fuel flow control valve 20 according to the number of ignitions of the burner.
This is an opening setting device.

Here, the operation of the above device will be explained with reference to the time charts shown in FIGS. 18(a) to (6). Figure 18 (α) shows the change in the amount of fuel input over time, Figure 18 (b) shows the change in the opening degree of the superheater bypass valve 5 over time, and Figure 18 (c) shows the change in the opening of the turbine bypass valve over time. 18 (d) shows the change in steam pressure over time, and FIG. 18 (g) shows the change in superheater outlet steam temperature over time. Time to is the ignition time, time t1 is the boost completion time, time t2
is the temperature rise completion time, and time t3 is the turbine ventilation time. Further, po is the initial steam pressure, and pl is the target pressure increase value. After the ignition at time to, the number of ignitions of the burner 2 is increased in stages, and the opening setting device 2 is increased accordingly.
The opening degree of the fuel flow M control valve 20 is controlled by the opening degree signal from 1, and the amount of fuel input increases stepwise as shown in FIG. 18 (α).

On the other hand, the signal switching device 18 is in a state in which the switching piece 18c is switched to the terminal 18b side before the steam pressure reaches the pressure increase target value p1. Therefore, the opening degree of the turbine bypass valve 10 is controlled by the output of the function generator 16 corresponding to the steam pressure until the steam pressure detected by the steam pressure detector 11 reaches the boost target value p1. It is uniquely determined by the steam pressure. Then, the turbine bypass valve 10, as shown in FIG. 18(c),
Before turbine ventilation time t3, its opening degree is controlled to release increasing steam pressure. Also, while the steam pressure is low, the saturation temperature of the steam is low, and the steam separator 4 is connected to the superheater 5.
Since low-humidity steam is supplied from the function generator 16, the output signal of the function generator 16 becomes a signal that increases the opening degree of the superheater bypass valve 9. Accordingly, the opening degree of the superheater bypass valve 9 increases as shown in FIG. 18(b). It becomes larger as shown in . Thereby, low-temperature steam is released, the amount of steam passing through the superheater 5 is reduced, and the outlet steam temperature of the superheater 5 is increased.

After the steam pressure reaches the boost target value p1, the switching piece 18e of the signal switching device 18 is switched to the terminal 18α side,
Thereafter, the opening degree of the turbine bypass valve 10 is determined by a signal obtained by proportionally and integrating the pressure deviation signal between the pressure increase target value pl set in the steam pressure setting device 12 and the actual steam pressure detected by the steam pressure detector 11. , is controlled as shown in FIG. 18(c). Furthermore, after the boost completion time tl, if the steam pressure becomes too high to be released by the turbine bypass valve 10, the output signal of the proportional integrator 15 also becomes large, so the high signal selector 19 selects that output signal. Then, the opening degree of the superheater bypass valve 9 is increased to allow steam to escape, thereby suppressing a rise in steam pressure.

Now, such a conventional device has the following six problems. This will be explained in order.

(1) With conventional devices, it is difficult to set optimal temperature and pressure increase patterns. Here, the optimal temperature and pressure increase pattern refers to a startup mode that increases temperature and pressure in the shortest possible time while suppressing the occurrence of thermal stress in thick-walled parts of the boiler device. By the way, in general, the most important thick-walled parts in a boiler device are the outlet header of the superheater 5 and the steam/water separator 4 (or drum), so the optimal temperature and pressure increase pattern is, in other words, The rate of change in the steam temperature at the outlet of the superheater 5 (hereinafter referred to as temperature increase rate), which affects the thermal stress of the outlet header of the steam separator 4 (or drum), and the thermal stress of the steam separator 4 (or drum) through the saturation temperature change. This can be said to be an embodiment in which the rate of change in steam pressure (hereinafter referred to as pressure increase rate), which has an influence on the temperature, is maintained at a permissible limit value for the rate of change in order to suppress generated thermal stress.

Looking at the conventional device described above from this perspective, in the conventional device, the temperature increase rate and pressure increase rate are determined by the function generator 16.1.
However, in order to make these settings, it is necessary to repeatedly carry out start-up tests on actual cans, which is troublesome and requires a lot of effort. Furthermore, upon startup, the steam pressure (initial pressure) at the ignition time to
If the steam pressure is different from that at the time of adjustment, a situation will occur where the temperature increase rate and pressure increase rate will deviate from the planned rate. In order to prevent the occurrence of such deviations, the function generator 16 in the conventional device
．． 17 is set with the aim that the temperature increase rate and pressure increase rate do not exceed the limit values at any stage of the temperature increase and pressure increase process, no matter what initial pressure is started. As a result, the temperature and pressure increase pattern deviates significantly from the optimal temperature and pressure increase pattern, and the startup time becomes considerably longer than when the temperature and pressure increase are optimal.

■ With conventional devices, it is difficult to reduce startup loss.

In the boiler apparatus shown in FIG. 17, when starting at a given temperature increase rate and pressure increase rate, the fuel flow control valve 20
The combination of the input fuel amount to be passed through, the opening degree of the superheater bypass valve 9, and the opening degree of the turbine bypass valve 10' is not determined on a penny.

That is, for example, while there is a combination in which a large amount of fuel is injected into the burner 2 and a large amount of steam is extracted from the superheater bypass valve 9 and the turbine bypass valve 10, there is also the opposite combination. Among these combinations, the six combinations that can maintain the given temperature increase rate and pressure increase rate and minimize the opening degree of the fuel flow control valve 20 have the same startup time. This is the operation with the least startup loss in achieving this. However, in the conventional device, the superheater bypass valve 9 and the turbine bypass valve 10
Since there is no function to operate the fuel flow rate control valve 20 in a coordinated manner, the opening setting device 21,
There is no alternative but to adjust each function generator 16, 17 individually. In reality, it is almost impossible to adjust these so that the above-mentioned optimal temperature increase rate and pressure increase rate are maintained and the startup loss is minimized.

(6) In the conventional device, even if the temperature increase and pressure increase pattern becomes abnormal due to disturbance or the like, no corrective action is performed to correct this. In other words, in conventional equipment, although the rate of temperature rise and the rate of pressure rise are important state quantities that govern the thermal stress in the thick walled parts of the boiler equipment, there is no means to measure them, and the control is left unchecked. It is in.

For this reason, even if the temperature increase rate and pressure increase rate deviate from the pattern planned when adjusting the opening setting device 20 and the function generators 16 and 17 due to, for example, disturbance, this cannot be corrected. Therefore, from this point of view, the opening degree setting device 20. When adjusting the function generators 16 and 17, it is necessary to plan the temperature increase rate and pressure increase rate to be low in consideration of a margin for suppressing generated thermal stress, which is a limiting factor in shortening the startup time.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to solve the above-mentioned conventional problems and to suppress the thermal stress generated in the thick-walled part of the boiler when starting the boiler. An object of the present invention is to provide a boiler startup control device that can complete the process in a short time and reduce startup loss.

[Summary of the invention]

In order to achieve the above object, the present invention detects steam temperature and steam pressure, and controls the boiler based on these values, a pressure increase target value, a temperature increase target value, a saturation temperature change rate limit value, and a temperature increase rate limit value. The steam temperature change rate target value and steam pressure change rate target value necessary for suppressing thermal stress in the thick-walled part of the It is characterized by providing a means for calculating each operation amount of the fuel flow rate control valve, and in addition to this feature, the operation amount obtained by this calculation is used to calculate the rate of change in steam temperature and the rate of change in steam pressure. It is also characterized in that the correction is made based on.

[Embodiments of the invention]

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 1 is a system diagram of a boiler startup control device according to an embodiment of the present invention. In the figure, parts that are the same as those shown in FIG. 17 are given the same reference numerals, and explanations thereof will be omitted. 25 is a steam temperature detector that detects the temperature of steam from the superheater 5. 26
18(d) is a boost target value setter for setting the boost target value p1 shown in FIG.
This is a temperature increase target value setting device that sets the outlet steam temperature. 2
Reference numeral 8 denotes a saturation temperature change rate limit value setting device for setting a saturation temperature change rate limit value for suppressing thermal stress in the thick walled portion of the steam/water separator 4; This is a temperature increase rate limit value setting device that sets a temperature increase rate limit value for suppressing thermal stress. Reference numeral 30 denotes a rate-of-change target value calculating device, into which the detected values of the steam pressure detector 11 and the steam temperature detector 25, and each setting value set in each setting device 26, 27, 28, 29 are input, and these values are calculated. A temperature increase rate target value signal α and a pressure increase rate target value signal S obtained by performing predetermined calculations and control based on are output (the configuration and operation of this rate of change target value calculation device 60 will be described later. The same applies to the optimal manipulated variable calculation device 40 and corrected manipulated variable calculation device 60, which will be described next.) Reference numeral 40 denotes an optimum operation amount calculation device, which calculates the detected values of the steam pressure detector 11 and the steam temperature detector 25, the temperature increase rate target value signal α and the pressure increase rate target value signal obtained by the rate of change target value calculation device 60. The fuel flow rate control valve opening command signal c2 and superheat 50 obtained as a result are calculated and controlled based on the above data and in accordance with a predetermined formula. A differentiator 51 compares the boost rate obtained by the differentiator 50 and the boost rate target value signal a, and outputs a boost rate deviation signal f which is the deviation thereof. It is. Also, 5
2 is a differentiator that inputs the detected value of the steam temperature detector 25 and differentiates it to calculate the actual temperature increase rate; 53 is a differentiator 52
Compare the temperature increase rate obtained with the temperature increase rate target value signal b,
This is a wattage reducer that outputs a heating rate deviation signal I that is the deviation. 60 is a correction operation amount calculation device, which receives each opening command signal c2.
d2. e2 is the deviation signal f.

I is corrected by predetermined calculation and control, and corrected opening command signals c2/, d, /, e2/ are output.

Next, the operation of this embodiment will be explained by the rate of change target value calculation device 30,
Optimal manipulated variable calculation device 40 and corrected manipulated variable calculation device 60
This will be clarified by explaining its configuration and operation.

First, the configuration of the rate of change target value calculation device 30 will be explained with reference to the system diagram shown in FIG. In FIG. 2, the same parts as those shown in FIG. 1 are given the same reference numerals. 31 is a subtracter that calculates the difference between the detected value of the steam pressure detector 11 and the pressure increase target value set in the setting device 26, and 32 is a function generator that outputs a value corresponding to the output signal of the subtracter 31. . The characteristics of function generator 62 are shown in FIG. 63 is a function generator that outputs a value corresponding to the detected value of the steam pressure detector 11, and its characteristics are shown in FIG.

34 is a multiplier that multiplies the saturation temperature change rate limit value set in the setting device 28 by the value obtained by the function generator 36;
5 is a low signal selector that selects and outputs the smaller value between the value of the multiplier 64 and the value obtained by the function generator 32. 36 is the detected value of the steam temperature detector i device 25 and the setting device 2
a subtractor that calculates the difference between the temperature increase target value set in 7 and 3;
7 is a function generator that outputs a value corresponding to the output signal of the subtracter 36; 38 is a function generator that outputs the smaller value of the value obtained by the function generator 37 and the heating rate limit value set in the setting device 29; It is a low signal selector that selects and outputs. The characteristics of the function generator 37 are shown in FIG.

Next, the operation of the rate of change target value calculation device 30 will be explained. The value output from the subtractor 51 is a pressure deviation signal that is the difference between the actual steam pressure and the target pressure increase value. This pressure deviation signal is input to the function generator 32, and the function generator 62 outputs a corresponding value. As is clear from the characteristic diagram of the function generator 32 shown in FIG. 3, when the steam pressure is far from the boost target value after the ignition point as shown in FIG. 18(d), the pressure deviation signal becomes large. Correspondingly, the boost rate basic target value signal output from the function generator 32 increases. That is, in this case, the basic target value of the boost rate, which is the basis of the target value of the boost rate, is set to the largest possible rate of change, thereby shortening the boost time. On the other hand, as the time of completion of pressure increase approaches and the steam pressure becomes close to the target value of pressure increase and the pressure deviation signal becomes smaller, the basic target value signal of the pressure increase rate becomes smaller as shown in the characteristic diagram of Fig. 3, which prevents overshoot. To prevent.

The detected value of the steam pressure detector 11 is also input to a function generator 63, which outputs a conversion signal corresponding to the saturation temperature change rate converted into a pressure change rate.

This conversion converts the saturation temperature change rate limit value set in the setting device 28 into a pressure change rate limit value, and for control purposes,
This is done because focusing on the steam pressure, which corresponds one-to-one to the saturation temperature, reduces the delay in control response and is also advantageous in terms of the resolution of the detector. The multiplier 64 outputs the converted pressure change rate limit value signal. The low signal selector 65 compares the pressure increase rate basic target value signal outputted from the function generator 32 and the pressure change rate limit value signal outputted from the multiplier 64, and selects the lower value for safety. This is output as a boost rate target value signal.

The detected value of the steam temperature detector 25 is input to a subtracter 36, and the difference from the temperature increase target value set in the setting device 27 is calculated. The temperature deviation signal output from the subtracter 66 is input to the function generator 37, and the function generator 37 outputs a basic target temperature increase rate value according to the characteristics shown in FIG. The above characteristics make it possible to set the basic target value for the temperature increase rate, which is the basis of the target value for the temperature increase rate, when the temperature deviation is large, that is, when the steam temperature is far from the target temperature value at the time of completion of heating. The rate of change is as large as possible, thereby shortening the heating time; conversely,
When the steam temperature approaches the temperature increase target value and the temperature deviation becomes small, the temperature increase rate basic target value is reduced to prevent overshoot. The low signal selector 38 is the function generator 3
The temperature increase rate basic target value signal output from 7 is compared with the temperature increase rate limit value signal set in the setting device 29, the lower value is selected for safety, and this is used as the temperature increase rate target value signal. Output as α. In the end, the change rate target value calculation device 30 determines the optimal pressure increase rate and temperature increase rate, and outputs them as the pressure increase rate target value signal b and the temperature increase rate target value signal α.

Next, the configuration of the optimum manipulated variable calculation device 40 will be explained with reference to the system diagram shown in FIG. In the figure, 11.25 is the third
These are the steam pressure detector and steam temperature detector shown in the figure. 41
is a plant characteristic calculation section. This plant characteristic calculation unit 41 calculates the rate of change target value calculation device 60 in the state of the boiler given by the value detected by the steam pressure detector 11 and the value detected by the steam temperature detector 25, and outputs a command signal. The amount of fuel input, the flow rate passing through the superheater bypass valve, and the flow rate passing through the turbine bypass valve are calculated to achieve the temperature increase rate target value and pressure increase rate target value output as α, b. This calculation will be described later. 42 is a plant characteristic calculation unit 4
This is a function generator which inputs the fuel input amount signal c1 of No. 1 and calculates the opening degree of the fuel flow rate control valve according to the characteristics shown in FIG. The determined opening degree is output as a fuel flow rate control valve opening command signal C2. 46 is a function generator having pressure-flow characteristics of the superheater bypass valve 9 as shown in FIG. 8, which inputs the detected value of the pressure detector 11 and outputs a value corresponding to this according to the characteristics. .

44 is a divider which inputs the superheater bypass valve passing flow rate signal d1 outputted from the plant characteristic calculating section 41 and divides it by the output of the function generator 46.

45 is a function generator having the characteristics shown in FIG. 9, which inputs the signal from the divider 44 and outputs a superheater bypass valve opening command signal d2 in response thereto.

Reference numeral 46 denotes a function generator having pressure-flow characteristics of the turbine bypass valve 10 as shown in FIG. 10, which inputs the detected value of the pressure detector 11 and outputs a value corresponding to the characteristic. . 47 is a turbine bypass valve passing flow rate signal e1 output from the plant characteristic calculation unit 41
This is a divider that inputs and divides it by the output of the function generator 46. 48 is a function generator having the characteristics shown in FIG. 11, which inputs the signal from the divider 47 and outputs a turbine bypass valve opening command signal e2 in response thereto.

Here, before explaining the operation of the optimum manipulated variable calculation device 40, the calculation of the plant characteristic calculation section 41 will be described. First, the symbols used in calculations are fixed as follows.

A: Heat transfer area of superheater 5 [d] GWW: Water supply ffi to water wall 1 (kg/5) G8: Evaporation 11 (kg/s) of water wall 1 A'CP): Saturated water enthalpy (k, I/~) (function of P) hN(P): Saturated vapor enthalpy (7/9) (
(Function of P) H (P,, T): Steam enthalpy at the outlet of the superheater 5 [IQI/J19] (Function of P, T) I (: Rate of change of steam enthalpy at the outlet of the superheater 5 [kr2J/kqs
) Hi: Inlet steam enthalpy of superheater 5 (1 cal 7
kg) HWw: Outlet fluid enthalpy of water wall 1 (W/
kg) Hmoo: Outlet water supply of the energy saver 6 x Ntarhi (m
at/Ir9)P: Steam pressure (kg/crl ab
s) p: Steam pressure change rate [kg/cP18] Q(++
): Heat absorption amount of water wall 1 [day/Jl) (function of Z) T: Steam temperature at outlet of superheater 5 ('C) Φ: Rate of change in steam temperature at outlet of superheater 5, C/8]v ( P
, T): average specific volume of steam in the superheater 5 Ct, l/~
] V: Volume inside the superheater 5 (, /) X: Fuel input amount [kg/8] Zmin: Fuel input amount lower limit value Ckp/s] V: Passing steam of the turbine bypass valve 10! , (kg/S) 1/min 'Minimum amount of steam passing through the turbine bypass valve 10 Cky/s] 2: Steam passing through the superheater bypass valve 9 11 (kg/#) α
: Average heat transfer coefficient (kal/ig'c) of superheater 5 TH (
Z): Temperature of combustion gas at the inlet of superheater 5 C) (Z
Among the above values, the heat transfer area A of the superheater 5 and its volume V are determined by the boiler structure, and the water supply amount G to the water wall 1 is determined by the boiler structure.
The lower limit value 2□i7 of the WW1 fuel input amount and the minimum value utnin of the amount of steam passing through the turbine bypass valve 10 are values determined by design. Further, the steam pressure P and the steam temperature T are values detected by the steam pressure detector 11 and the steam temperature detector 25, respectively, and the steam pressure change rate and the steam temperature change rate φ are the values detected by the rate of change target value calculation device. Output signal α from 30.

given by b. Furthermore, the saturated water enthalpy A'(
P), saturated steam enthalpy h, outlet steam enthalpy of the superheater 5 H(P, T), and steam inside the superheater 5 can all be determined using a steam table based on the steam pressure P1 and the steam temperature T.

Now, regarding heat transfer in the superheater 5, the following equations hold true.

・・・・・・・・・・・・■ In this embodiment, the superheater bypass valve 9 is connected to the steam separator 4.
Since it is connected to the outlet of the superheater 5, the inlet steam enthalpy H1 of the superheater 5 is H4-A'ω)
(3) If the superheater bypass valve 9 is connected to the middle of the superheater 5, the temperature at that point is detected, and the temperature is calculated from this and the steam pressure P. The enthalpy (1) can be found using the steam table. Furthermore, the average heat transmission coefficient α of the superheater 5 is strictly a function of the combustion gas temperature and the combustion gas amount, both of which are functions of the fuel input fix. The current value of the input amount may be actually measured and given as a function thereof.

From equations (1), ■, and (3) above, 10A aTn(z) −A aTJ
(4) Equation (4) can be rewritten as the following equation.

'i' −−Kl−y+KzlH(z)−Ks・Mountain・・K15) Here, 3 in KlIK21 is a model parameter, which is defined as (6).

Furthermore, the following equations hold true regarding steam pressure and heat transfer through the water wall 1.

VP=G6-y-g・・・・・・・・・・・・
...(9) In addition, the outlet water supply enthalpy of the economizer B is HEO
O is approximately a constant value at startup, but if necessary, the temperature of the feed water at the outlet of the economizer 6 may be actually measured and determined based on this value and the steam pressure P using a steam table.

From the above equations (9), αo), and (u), ·············(B) Equation (b) can be rewritten as the following equation.

P=4(y z)+Ks ・Q(2+) Ke
=・= (18) Here, Ka + Ks + Ks
is a model parameter and is defined as . And θ3
), and the amount of steam 2 passing through the superheater bypass valve 9 is 2≧0 due to its properties.
... Mon, Chu, (2)), so by substituting formula 09 into formula (e), p≦4・y + Ks・Q(a;) K
s ・------OR).

From the above, the function of the plant characteristic calculation unit 41 comes down to solving the following mathematical programming problem.

That is, the minimum value X that satisfies the constraints of each of the above equations is found, and for that value 2, the value &+g is found from equations (5) and (17) above. The solution to this problem is illustrated in FIG. 12.

FIG. 12 is a graph showing the solution of the above calculation by the plant characteristic calculation section. In the figure, the horizontal axis represents the fuel input amount X, and the vertical axis represents the amount of steam passing through the turbine bypass valve 10, V.

The illustrated straight line B1 indicates the minimum value V in of the amount of steam passing through the turbine bypass valve 10, and the straight line B2 indicates the lower limit value rjmin of the fuel input amount. Furthermore, the curve Es
The curve B4 corresponds to a rewritten equation of Equation (5), and curve B4 corresponds to a rewritten equation of Equation (5). Then, the set of solutions that satisfy the above constraints lies on the curve B4 and the straight line Bl
, B2 and curve B3, which fall within the 'area' within the diagonal lines. In this case, the optimal solution sought is indicated by a dot.

This concludes the explanation of the calculation in the plant characteristic calculation unit 41, and next, the operation of the optimal manipulated variable calculation device 40 will be explained in the thirteenth section.
The explanation will be given with reference to the fugastric chard shown in the figure. First, the plant characteristic calculation unit 41 calculates the value Ta(z)
is an upwardly convex monotonically increasing function, and Q (z) is also a monotonically increasing function with at most one inflection point (the point where the second-order differential coefficient becomes 0), so the procedure shown in Figure 16 The optimal solution can be obtained. First, the steam temperature change rate Φ and the steam pressure change rate S obtained by the change rate target value calculating device 30, the value P detected by the steam pressure detector 11, and the value T detected by the steam temperature detector 25. (Step Sl). Next, based on the values P and T, (6), (7
) , (8) , (1→, elevation L Parameter Kl according to equation (16).

Calculate K2, K3, , i(a, Kg, Kg (step 82). Using these parameters, find the solution (machi, yo) of the following simultaneous equations (hand MSs).

Then, j solutions of the following simultaneous equations (zx, i/+
) −(22+1/2) +・・・・・・・・・
......(2X,, y7) is determined (step S4).

Furthermore, the solution of the following simultaneous equations (Z j+1, 11j+1
) is determined (step S5).

Once the solutions are obtained from the above, next, these solutions 11+
1. Sort x2-0-°゛°HgIJj, zz+1 in descending order, take out the smallest one, remove its subscript, and create the value z7. The extracted value II+7 is the value “tni”
It is compared whether it is greater than or equal to rn (step 87), and the value π7
is less than the value xmin, then the value ffl! +
Z2 + "" m j + gej + 1,000, step S6
The next largest value after 7 is extracted, and this value is set as a new value x7 (step Sg). Step 8B
The new value 2 taken out is again compared with the value "min" (step 87).

In this way, t continues until values z and n of 2 or more are obtained.
yitga.

Step 87. Sg is repeated. In this way,
In step S7, the minimum value zt above the value 2+frLin
Once L is obtained, the value v1 corresponding to the minimum value ZtL, that is, the values v, rL, is extracted from the solution obtained earlier, and the values v, n are compared with the value vml. (Step 8e). If the value v7 is less than the value '/min, the procedure returns to the Sagi step S8 again, the next largest value after the minimum value ZtL is taken out, this value is set as the new value z7, and the step 87+so is repeated. will be returned. In this way, finally, among the solutions that are greater than or equal to the value "rnifL and greater than or equal to the value -i," the value 11+7 where the value π is the smallest and the corresponding value V are obtained. It is determined whether the solution (" 3 + y, L) satisfies the following equation (Step 8to).

If it is determined in step 810 that the above relationship is not satisfied, the process returns to step S8 again and steps 87-8e +81
Repeat 0. Then, when the relationship of the above formula is satisfied in step 810, the procedure moves to 811, and the calculation of the following formula is executed.

2=1(Ka ・Q (Zs) PKs)
ys Through this calculation, the optimum fuel input amount ZfL, the amount of steam passing through the turbine bypass valve 10, and the passing steam ig of the superheater exhaust valve 9 are obtained, and the plant characteristic calculation unit 4
1 outputs a signal C1+ 4+ el corresponding to these quantities 'z, , Z + u, n.

Returning to FIG. 3, the fuel input amount signal c1 is input to the function generator 42, which outputs an opening command value for the fuel flow rate control valve 20 according to the characteristics shown in FIG. In this case, since the fuel flow rate control valve 20 can normally be considered to have a constant differential pressure before and after the control valve 20, the fuel flow rate can be adjusted by directly inputting the fuel input amount signal C1 to the function generator 42. An opening command signal C2 for the control valve 20 is obtained. On the other hand, since the valve inlet pressure of the superheater bypass valve 9 and the turbine bypass valve 10 changes as the pressure increases, each valve 9.10
It is necessary to take this into account when converting the opening degrees of the valves 9 and 10. For this reason, the opening degrees of each valve are determined once the pressure-flow characteristics of each valve 9 and 10 are determined. That is, the steam pressure detected by the steam pressure detector 11 is
3, the flow rate is converted into a flow rate corresponding to the input according to the characteristics shown in FIG. Therefore,
Superheater bypass valve 9 obtained by plant characteristic calculation unit 41
A divider 44 divides the passing flow rate by the converted flow rate. As a result, the necessary boat area value of the superheater bypass valve 9 is output from the divider 44. This area value is input to the function generator 45, and the function generator 45 outputs the opening command signal d2 of the superheater bypass valve 9 necessary to obtain the boat area in accordance with the characteristics shown in FIG. Ru. In exactly the same way, the function generator 46 outputs the first
A flow rate corresponding to the steam pressure is output according to the characteristics shown in FIG. 10 necessary boat area values are input to the function generator 48, and the function generator 48 generates an opening command signal e2 of the turbine bypass valve 10 necessary to obtain the boat area in accordance with the characteristics shown in FIG. is output. It should be noted that by using the calculation results of the optimum operation amount calculation device 40, it is also possible to output an alarm signal of an abnormal state, and it is also possible to obtain historical data of life prediction.

This completes the explanation of the configuration and operation of the optimum manipulated variable calculation device 40, and finally the system diagram shown in FIG. 14 and the characteristic diagram shown in FIG. This is explained by: The corrected manipulated variable calculation device 60 uses the fuel flow rate control valve 2 obtained by the optimal manipulated variable calculation device 40.
0 opening command signal C2 + opening command signal d2 of the superheater bypass valve 9 and opening command signal e2 of the turbine bypass valve 10 as an opening command signal in accordance with the actual opening of each valve 20, 9.10. Correct to C2'l d2'+62'. This correction is based on a pressure increase rate deviation signal based on the actual steam pressure and steam temperature detected by the steam pressure detector 11 and steam temperature detector 25! and heating rate deviation signal g
It is done by.

Here, these pressure increase rate deviation signal f and temperature increase rate deviation signal g are obtained by the aforementioned differentiator 50.degree. 52 and subtractor 51.53 shown in FIG. That is, steam pressure detector 1
The detected value of 1 is input to a differentiator 50, and an actual boost rate signal is obtained from the differentiator 50. The subtracter 51 inputs this boost rate signal and the boost rate target value signal S from the change rate target value calculation device 60, and generates a boost rate deviation signal f which is a signal of the difference.
Output. Similarly, the differentiator 52 inputs the steam temperature detected by the steam temperature detector 25 and outputs an actual temperature increase rate signal, and the subtractor 56 uses this temperature increase rate signal and the rate of change target value calculation device 30. inputs the temperature increase rate target value signal α from , and outputs a temperature increase rate deviation signal I which is a signal of the difference.

FIG. 14 is a system diagram of the correction operation amount calculation device.

In the figure, 61.62 is the boost rate deviation signal! 63 and 64 are proportional integrators that input the heating rate deviation signal I and output the proportional integral value. 65 is a subtracter that inputs the signals of the proportional integrators 61 and 63 and outputs the difference between the two, 66 is an adder that corrects the opening command signal d2 of the superheater bypass valve 9 with the signal of the subtractor 65, and 67 is a An adder 68 that adds the signals of the proportional integrators 62 and 64 is an adder that corrects the opening command signal e2 of the turbine bypass valve 10 with the signal of the adder 67. 69 is a function generator having the characteristics shown in FIG. 15, which inputs the signal from the adder 68 and outputs a signal corresponding thereto. 70 is the opening command signal C2 of the fuel flow rate control valve 20
This is an adder that corrects the function generator 69 using the signal from the function generator 69.

Here, the operation of the corrected manipulated variable calculation device 60 will be explained. As is clear from Sagi's explanation, each opening command signal c21 d2 + obtained by the optimum operation amount calculation device 40
62 are all obtained by approximating the plant characteristics, and such opening command signals 12+ d2+
Even if an actual plant is operated using e2, there is a risk that the intended operation will deviate. Therefore, the correction manipulated variable calculation device 60 inputs the deviation signals j and tt between the calculated temperature increase rate target value and pressure increase rate target value and the actual temperature increase rate and pressure increase rate, and performs an operation to reduce this deviation. Opening command signal C for each valve
2+ d2. This is intended to correct e2.

By the way, in general, when the turbine bypass valve 10 is opened, both the temperature increase rate and the pressure increase rate decrease, and when the superheater bypass valve 9 is opened, the temperature increase rate increases, while the pressure increase rate decreases. This means that when trying to lower the temperature rise rate deviation signal 11 pressure rise rate deviation signal f, if one deviation signal is used to correct one valve, for example, the temperature rise rate deviation signal g is used to bypass the superheater. This shows that if an attempt is made to correct the opening degree of the valve 9 and also to correct the opening degree of the turbine bypass valve 10 using the pressure increase rate deviation signal f, it will always cause a disturbance to the other. In order to reduce this disturbance as much as possible, when reducing the temperature increase rate, the superheater bypass valve 9 is closed and the turbine bypass valve 10 is opened at the same time to keep the total amount of steam passing through each valve 9 and 10 constant. It is necessary to prevent any disturbance from occurring to the pressure increase rate, and conversely, when reducing the pressure increase rate, the superheater bypass valve 9 is also opened at the same time as the turbine bypass valve 10 is opened, to prevent the temperature increase rate from decreasing due to disturbances. It is necessary to compensate for this. Correction operation amount calculation device 60 shown in No. 141iU
is designed with these things in mind.

In FIG. 14, the opening command signal d2 of the superheater bypass valve 9 is corrected as follows.

That is, the boost rate deviation signal f output from the proportional integrator 61
The correction signal based on the temperature increase rate deviation signal I output from the proportional integrator 66 is input to the subtracter 65,
For the above-mentioned reason, a correction signal for the opening degree of the superheater bypass valve 9 is obtained by subtracting the latter from the former. Subtractor 65
The correction signal from
The adder 66 outputs the corrected opening command signal d2pa for the superheater bypass valve 9. Further, the opening command signal e2 of the turbine bypass valve 10 is corrected as follows. That is, the correction signal based on the boost rate deviation signal I output from the proportional integrator 62 and the correction signal based on the temperature rise rate deviation signal I output from the proportional integrator 64 are input to the adder 67, and for the above-mentioned reason, both are input to the adder 67. is added to obtain an opening correction signal for the turbine bypass valve 10. The correction signal from the adder 67 is added to the opening command signal e2 in an adder 68, and the adder 68 outputs the corrected opening command signal e2/ of the turbine bypass valve 10.

Next, correction of the opening degree command signal C2 of the fuel flow rate control valve 20 will be described. As described above, the opening command signal d2 of the superheater bypass valve 9 and the turbine bypass valve 10. e2
When correcting the amount of fuel input, if the amount of fuel input is also corrected at the same time,
There is a possibility that the correction operations will interfere with each other. Therefore, in order to avoid such interference, the amount of fuel input is basically determined based on the opening command signal c obtained by the optimum manipulated variable calculation device 40.
2 is used as is, but the amount of fuel input is reduced or increased only when the opening degree of the turbine bypass valve 10 reaches an extremely large value or an extremely small value. Such an operation is obtained by the characteristics of the function generator 69 shown in FIG. That is, the function generator 69 generates the actual opening command signal e of the turbine bypass valve 10.
2/ is input, a correction signal is output only when this signal e 2/ is extremely large and only when it is extremely small, and the adder 70 adds it to the opening command signal c2 to correct the fuel flow rate control valve 20. Opening command signal c
We get 2'.

In this way, the opening command signals c2', t12', and g2' obtained by the correction operation amount calculation device 60 are used to actually operate the fuel flow control valve 20, superheater bypass valve 9, and turbine bypass valve 10, respectively. output as an opening command.

The operation of this embodiment has been explained above by explaining the configuration and operation of each part.Finally, the operation of this embodiment can be summarized as follows based on FIG. first,
The rate of change target value calculation device 60 inputs the actual steam pressure and actual steam temperature detected by the steam pressure detector 11 and the steam temperature detector 25, and inputs the actual steam pressure and the actual steam temperature detected by the steam pressure detector 11 and the steam temperature detector 25, and also inputs the actual steam pressure and the actual steam temperature detected by the steam pressure detector 11 and the steam temperature detector 25, and inputs the actual steam pressure and the actual steam temperature detected by the steam pressure detector 11 and the steam temperature detector 25, and also inputs the actual steam pressure and the actual steam temperature detected by the steam pressure detector 11 and the steam temperature detector 25, and inputs the actual steam pressure and the actual steam temperature detected by the steam pressure detector 11 and the steam temperature detector 25, as well as inputs the actual steam pressure and the actual steam temperature detected by the steam pressure detector 11 and the steam temperature detector 25, and inputs the actual steam pressure and the actual steam temperature detected by the steam pressure detector 11 and the steam temperature detector 25.
Enter the value set to 27°28.29. and,
The pressure is increased based on the steam pressure, the target pressure increase value set in the setting device 26, and the saturation temperature change rate limit value set in the setting device 28 (a value that takes into account the thermal stress of the steam-water separator 4, which is a thick wall part). The rate target value signal is calculated and output, and also calculates and outputs the steam temperature, the temperature increase target value set in the setting device 27, and the temperature increase rate limit value set in the setting device 29 (the Temperature increase rate target value signal α based on the value that takes into account the thermal stress of the header
is calculated and output.

The optimum operation amount calculation device 40 uses these temperature increase rate target value signals α
, Pressure increase rate target value signal b1 Inputs the measured steam pressure and measured steam temperature, derives the required formula based on these values and plant characteristics, and by solving such a formula, suppresses thermal stress in the thick wall part. Moreover, the optimum fuel input amount, superheater bypass valve passage flow rate, and turbine bypass valve passage flow rate are determined in order to complete the start-up in a short time and reduce the start-up loss. These values are determined by the opening degree of the fuel flow control valve 20 and the superheater bypass valve 9, respectively.
and the opening of the turbine bypass valve 10, and the opening command signal 62+d2. $2
is output rel.

The differentiators 50 and 52 output the rate of change in the steam pressure and steam temperature detected by the steam pressure detector 11 and the steam temperature detector 25, that is, the actual pressure increase rate and temperature increase rate. These pressure increase rate and temperature increase rate are compared with the calculated pressure increase rate target value signal S and temperature increase rate target value signal α by a subtractor 51.53,
From the subtracters 51 and 53, boost rate deviation signals, which are the difference between the two, are output! and a temperature increase rate deviation signal I are output.

The correction operation amount calculation device 60 receives the boost rate deviation signal! and the temperature increase rate deviation signal g, the optimum manipulated variable calculation device 40
Each opening command signal C2+ d2+ 6 output from
2 is corrected so that no disturbance occurs, and the corrected opening command signals c2', d2a e2' are output.

These opening command signals C2'+dz' and e2' control the fuel flow control valve 20 and the superheater bypass valve 9, respectively.
, the turbine bypass valve 10 is operated to achieve the objective.

As described above, in this embodiment, the external temperature rate target is set based on the steam pressure, steam temperature, and the pressure increase target value, temperature increase target value, saturation temperature change rate limit value, and temperature increase rate limit value set in the setting device. The optimal opening of the fuel flow control valve, superheater pipe valve, and turbine bypass valve is calculated based on the temperature increase rate target value, pressure increase rate target value, and the steam pressure and steam temperature. Since the opening of each valve is controlled by calculating the opening command value and correcting each opening command value appropriately, the thermal stress generated in the steam separator and the superheater outlet header when the boiler is started is reduced. The startup can be completed in a short time while being controlled, and the startup loss can be reduced.

FIG. 16 is a partial system diagram of a boiler startup control device according to another embodiment of the present invention. In the figure, 26 is a pressure increase target value setter, 27 is a temperature increase target value setter, and 30 is a rate of change target value calculation device, which are the same as those shown in FIG.

Temperature detectors 75 and 76 detect the inner metal temperature and outer metal temperature of the thick-walled portion of the steam/water separator 4, respectively;
Temperature detectors 7 and 78 detect the inner metal temperature and outer metal temperature of the thick walled portion of the superheater outlet header, respectively. 79 is a steam separator thermal stress monitoring and control device, and 80 is a superheater outlet header thermal stress monitoring and controlling device. gThis embodiment differs from the first embodiment in that the first embodiment has a saturation temperature change rate. While the limit value and temperature increase rate limit value are set in the setting device 28, 29 and input into the rate of change target value calculation device 30,
In this embodiment, the saturation temperature change rate limit value and the temperature increase rate limit value are input to the change rate target value calculating device 60 by other means. The other configurations and operations are the same as in the first embodiment.

The inner metal temperature and outer metal temperature of the steam/water separator 4 detected by the temperature detectors 75 and 76 are input to the control device 79. The control device 79 constantly calculates the thermal stress generated in the thick portion of the steam/water separator 4 based on these temperatures, and outputs an appropriate saturation temperature change rate limit value according to the generated thermal stress. Similarly, the inner metal temperature and outer metal temperature of the superheater outlet header detected by the temperature detectors 77 and 78 are input to the control device 80, and the control device adjusts the thick wall portion of the superheater outlet header based on these temperatures. It constantly calculates the thermal stress generated in the process, and outputs an appropriate temperature increase rate limit value according to the generated thermal stress.

In this way, in this embodiment, instead of the saturation temperature change rate limit value setter in the previous embodiment, a temperature detector for detecting the inner metal temperature and outer surface metal temperature of the thick part of the steam/water separator, and A steam/water separator thermal stress monitoring and control device is installed.
In addition, in place of the temperature increase rate limit value setting device, we installed a temperature detector that detects the inner metal temperature and outer metal temperature of the thick section of the superheater outlet header, and a superheater outlet header thermal stress monitoring and control device. , not only has the same effect as the example in Sagi, but also enables even more rapid startup when there is a margin for thermal stress, and conversely allows for slower temperature and pressure increases when thermal stress is abnormally high. It is possible to obtain a saturation temperature change rate limit value and a temperature increase rate limit value.

〔Effect of the invention〕

As described above, in the present invention, the temperature increase rate target value and the pressure increase are determined based on the detected steam pressure and steam temperature, the pressure increase target value, the temperature increase target value, the saturated temperature change rate limit value, and the temperature increase rate limit value. A valve that calculates a rate target value and controls the fuel supply amount based on the target value, the steam pressure, and the steam temperature, a valve that bypasses steam from the superheater, and a valve that extracts steam from the superheater to a source other than its main supply destination. By calculating the opening degree of the valve to open the boiler and then appropriately correcting this opening degree, it is possible to complete startup in a short time while suppressing thermal stress generated in the boiler thick-walled parts. Start-up loss can be reduced.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a boiler start-up control device according to an embodiment of the present invention, FIG. 2 is a system diagram of a rate-of-change target value calculation device shown in FIG. 1, and FIGS. 3, 4, and 5@ are characteristic diagrams of the function generator shown in FIG. 2, FIG. 3 is a system diagram of the optimal manipulated variable calculation device shown in FIG. 1, FIGS. 7, 8, 9,
Fig. 10 and Fig. 11 are characteristic diagrams of the function generator shown in Fig. 3, Fig. 12 is a graph showing the solution of the calculation of the plant characteristic calculation section shown in Fig. 3, and Fig. 13 is shown in Fig. 3. A flowchart explaining the operation of the plant characteristic calculation section, FIG. 14 is a system diagram of the pain relief operation amount calculation device shown in FIG. 1, FIG. 15 is a characteristic diagram of the function generator shown in FIG. 14, and FIG. A partial system diagram of a boiler starting device according to another embodiment of the present invention,
Figure 17 is a system diagram of a conventional boiler startup control device, Figure 18
Figure (α), ,Cb). (c), (d), and (g) are time charts showing changes in the pressure of each part when the boiler is started. 4... Steam water separator, 5... Superheater, 7... Turbine, 9... Superheater bypass valve, 10... Turbine bypass valve, 11... Steam pressure detector, 20... ... Fuel flow rate control valve, 26 ... Boost target value setting device, 27 ...
Temperature increase target value setter, 28...Saturation temperature change rate limit value,
29...Temperature increase rate limit value, 30...Change rate target value calculation device, 40...Optimum operation amount calculation device, 50.52...
・Differentiator, 51.53...Subtractor, 60...Correction operation amount calculation device Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 3 Fig. 7 Fig. 8 Fig. 9 Figure 1O Figure 11 Figure 12 Figure 13 Figure 14 6゜ Figure 17 Figure 18

Claims (1)

[Claims] 1. A superheater, a first valve that bypasses steam from the superheater, a second valve that extracts steam from the superheater to a location other than its main supply destination, and a fuel supply to the furnace. A boiler equipped with a third valve that controls the supply amount, a temperature detector that detects the steam temperature in a predetermined part of the boiler, a pressure detector that detects the steam pressure in the predetermined part, the steam temperature, Steam temperature change rate target value and steam pressure necessary to suppress thermal stress in a predetermined structural part of the boiler based on the steam pressure, pressure increase target value, temperature increase target value, saturation temperature change rate limit value, and temperature increase rate limit value. a first calculation means for calculating a rate of change target value; and a first calculation means for calculating a rate of change target value based on the steam temperature change rate target value, the steam pressure change rate target value, the steam temperature, and the steam pressure obtained by the first calculation means. 1. A boiler start-up control device comprising: second calculation means for calculating respective operation amounts of the first valve, the second valve, and the third valve. 2. A superheater, a first valve that bypasses steam from the superheater, a second valve that extracts steam from the superheater to a location other than its main supply destination, and a second valve that controls the amount of fuel supplied to the furnace. a temperature detector for detecting the steam temperature in a predetermined part of the boiler; a pressure detector for detecting the steam pressure in the predetermined part; and the steam temperature, the steam pressure, and a pressure increase target. calculate the steam temperature change rate target value and steam pressure change rate target value necessary for suppressing thermal stress in a predetermined structural part of the boiler based on the temperature increase target value, saturation temperature change rate limit value, and temperature increase rate limit value. and a first calculation means for determining the first valve and the first valve based on the steam temperature change rate target value, the steam pressure change rate target value, the steam temperature, and the steam pressure obtained by the first calculation means. a second calculation means for calculating each operation amount of the second valve and the third valve; and a second calculation means for calculating each operation amount of the second valve and the third valve, and each operation amount obtained by the second calculation means is calculated as a rate of change in the steam temperature and a rate of change in the steam pressure. 1. A boiler startup control device comprising: a correction means for correcting based on.